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Old 10-22-2011, 07:48 AM
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Cat removal

I have a 2001 chevy 2500hd 8.1 liter does it hurt the engine to remove the catalytic converters ? I know legaly Im not suposed to remove them but would like to ler it breath more.

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Old 10-22-2011, 09:27 AM
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Personally I would be hesitant to remove them.

Newer vehicles (newer than the crap I drive, anyway) have an oxygen sensor both upstream and downstream of the catalyst, so the computer will 'see' a problem now.

Modern catalysts are much more free-flowing compared to the horrid units first produced in the 70s.

A friend of mine ran his 2001 4.8 L 1/2 ton down the quarter with and w/o the converter in place and ran the exact same time. No saying that you will have the same experience but it hardly makes a good argument for chopping them out.
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Old 10-22-2011, 11:04 AM
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Cat removal

Mine only has the up stream sensors and they are up closer to the manifolds not down by the converters I just didnt know if it would hurt the engine to take them off
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Old 10-22-2011, 01:02 PM
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Better look at your exhaust again, since parts house catalogs show BOTH upstream and downstream O2 sensors for your truck. In any case, why bother to remove them? Even it it doesn't throw a code, there will be no benefit unless the substrate has melted down in each cat.
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Old 10-22-2011, 01:09 PM
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Quote:
Originally Posted by joe_padavano
Better look at your exhaust again, since parts house catalogs show BOTH upstream and downstream O2 sensors for your truck. In any case, why bother to remove them? Even it it doesn't throw a code, there will be no benefit unless the substrate has melted down in each cat.
The thing that would keep me from doing it is the prospect of a very large Federal fine for removing smog equipment. The other thing that would prevent it is that I know it's a bad idea to hot rod your daily driver. If you want to go fast, start a project with a car/truck that you don't have to drive every day. I've always liked swapping a V8 into a small sports car like an MGB. One evening at the drags, I teched an MGB street-driven roadster with a 460 Ford installed, so don't tell me it can't be done.
http://www.britishv8.org/Photos-MG-Conversions.htm
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Old 10-22-2011, 01:43 PM
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Quote:
Originally Posted by BBLK4X4
I have a 2001 chevy 2500hd 8.1 liter does it hurt the engine to remove the catalytic converters ?
No it won't.
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Old 10-22-2011, 02:17 PM
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Quote:
Originally Posted by BBLK4X4
I have a 2001 chevy 2500hd 8.1 liter does it hurt the engine to remove the catalytic converters ? I know legaly Im not suposed to remove them but would like to ler it breath more.
Leave them be. They flow well as Joe P said.
If you really want a little more ( I mean Little) performance,put on a dual exhaust from the cat back, and use an H or X pipe crossover. It will help a little, the sound will be worth it.
I see guys who gut their cats , and usually it is due to a mis diagnosis of the problem, then WE end up repairing the real problem, and they end up with the MIL lit up for days with a P0420 and P0430, that wont go away untill a new pair of cats is installed.
Unless they are plugged and you are so poor you cant pay attention, gutting a cat converter is UNHEALTHY , lots of time consuming work, and usually fails to deliver more than a nuisance with an MIL that wont go away.
The substrate inside is very BAD for your respritory system, leave the job for a proffesional.
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Old 10-23-2011, 08:30 AM
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Cats........

Hi,i removed the cat from my motor coach,cut it open,gutted it,welded it back togerther,and put it back on,picked up ABOUT 1/2 MPG,but,more power.(coach weigs 16,000 lbs.)
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Old 10-23-2011, 08:59 AM
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If you remove the cats you will need to have the computer reflashed to ignore the rear o2's
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Old 10-23-2011, 09:48 AM
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I don't know about your Chevy but I know that after a few experiences with AM converters we won't even put an AM one in let alone the thought of removing one altogether. If putting in an AM converter throws codes pulling one out should sure as heck do it.

But I am CLUELESS on these computer controlled cars. But the first time we replaced a cat with an AM and it had codes we couldn't clear, we then replaced it with an OEM and delivered the truck code free with not a hint of a problem we will stick to OEM converters.

Brian
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Old 10-23-2011, 10:16 AM
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If it's a carbed vehicle with a normal electronic ignition, say HEI or DuraSpark, I wouldn't hesitate removing a cat. With all the electronics/computer, that cat is a part of the system and is really needed for proper operation.
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Old 10-23-2011, 10:17 AM
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Quote:
Originally Posted by MARTINSR
I don't know about your Chevy but I know that after a few experiences with AM converters we won't even put an AM one in let alone the thought of removing one altogether. If putting in an AM converter throws codes pulling one out should sure as heck do it.

But I am CLUELESS on these computer controlled cars. But the first time we replaced a cat with an AM and it had codes we couldn't clear, we then replaced it with an OEM and delivered the truck code free with not a hint of a problem we will stick to OEM converters.

Brian
Could you share what brand of AM cat was giving you problems? I don't want to start some brand-loyalty flame war, so PM if you want. Just curious for future reference.

- Cameron
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Old 10-23-2011, 10:20 AM
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Ahhh,there you go, that makes sense. LOVE those carburetors!

Brian
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Old 10-23-2011, 10:44 AM
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With O2 sensor...

On vehicles with O2 sensors (all late model stuff) the cat actually does nothing for emissions UNLESS there is a fault with the computer, injectors, etc. The computer keeps the mixture so close to theoretically correct, the burn produces very little emissions. On my particular choice of hot rodding fodor, (Jag's) removing the converter does not affect the emissions. In CT since the cars I work on are over 25 yrs old, there is only the sniffer and they pass that with or without the cats. That said, the new cats are so free flowing, I don't see any reason to remove them. If you have O2 sensors after the cat (cats) you run the risk of throwing code constantly. I'd leave the cats in place if you have the second set of sensors.
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Old 10-23-2011, 11:33 AM
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[QUOTE=WildBill]On vehicles with O2 sensors (all late model stuff) the cat actually does nothing for emissions UNLESS there is a fault with the computer, injectors, etc. The computer keeps the mixture so close to theoretically correct, the burn produces very little emissions. [QUOTE]

Actually this is not correct. Not to start a pissin match , but for clarification.
A Cat converter converts Carbon Monoxide ( CO) (very toxic) and unburnt hydrocarbon (HC) (Toxic and nasty) along with unspent Oxygen (O2) to Carbon Dioxide ( CO2) and water ( H2O ). A close stoitch will aid in the process as mentioned above.
CO2 and H2O along with unspent oxygen and other atmospheric gases are not toxic to plants animals and humans.
Carbon monoxide is deadly to breath, kills most anything and is a major component of acid rain. Something to remember when waxing your car.
Leave your cats alone.It turns poison into plant food.(CO2)
A fault with the electronics or the emmission system is usually what kills a cat.
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